Well Steve was wearing his suit and had the shield so in universe it's a replica that isn't fully accurate(or Steve had various versions and this was the one he wasn't wearing).

And of course film wise I don't think they need to jump through hoops to explain one extra red stripe. But seeing as how Cap was kinda a secret, I think his original suit is not in the case and he steals a replica.

At the end of the day the The Avengers suit made Evans look smaller because it was tighter. For this film they made the suits puffier which makes him look bigger. In the Avengers, he looked big compared to Tony out of suit but next to Hulk, Thor,Iron Man and the Aliens, he came off as large as Hawkeye.

A lot of people have expressed their distaste for the navy blue suit we're going to see, and primarily for the "un-Americanness" of it. I think that will be addressed in the movie. They've done a really great job in TFA and in Avengers of showcasing the importance, not only to Steve, but in general, of having a red, white, and blue star-spangled uniform. I think the absence of it in the new version, the "shame" it represents to Steve and the public, will be a plot point.

Personally, I do like it as a uniform, but I'm excited to see him wearing the TFA throwback by the end of the movie.

I really like their take on the Super Soldier suit. Even though I agree it may lack some red other than the red stripes on the leg; I think it looks good. Gives a bit of size for Chris Evans since a lot complained he looked smaller in TA.

Seeing the Commander Rogers suit and the WWII suit in the trailers makes you think about how truly horrible the Avengers suit was.... I mean seriously what were they thinking? The actual body of the suit doesn't get much criticism, but I wasn't even a big fan of that part. But the cowl.... so bad. It looks like Marvel realized this, the new suit looks fantastic. I can't wait to see how Cap looks in Avengers 2

Seeing the Commander Rogers suit and the WWII suit in the trailers makes you think about how truly horrible the Avengers suit was.... I mean seriously what were they thinking? The actual body of the suit doesn't get much criticism, but I wasn't even a big fan of that part. But the cowl.... so bad. It looks like Marvel realized this, the new suit looks fantastic. I can't wait to see how Cap looks in Avengers 2

The problem with the suit in TA wasn't the actual visual details; it was the materials used that made it look cheap and unsuperhero-y. If they had used some more tactical-looking materials, then it would have been a fine suit.